The DeHavilland DH-2 Beaver aircraft, manufactured by DeHavilland Aircraft of Canada Ltd and first flown in 1947, was an STOL, single engine, metal, cabin monoplane transport designed principally for Canadian bush flying on floats, skis or wheels although the U.S. Army was a major purchaser of the type. The Beaver has been used for bush flying for many years. Although currently out of production, many of the 1700 Beaver aircraft built continue to be carefully maintained and used daily throughout the world, particularly in bush operations. The aircraft is known for its reliability and strength in such operations.
The DeHavilland DH-3 Otter aircraft, first flown in 1951, was also principally flown in bush operations as a utility transport with larger seating capacity than the Beaver. It likewise has a reputation for reliability and strength and many of the 460 aircraft manufactured continue to fly and are carefully maintained.
While the flying characteristics of the aircraft are very satisfactory, the several modifications according to the present invention have been discovered which, taken both singly and in combination, enhance the flight characteristics of both aircraft. While it is not known conclusively why these modifications produce such improved flying characteristics, the explanations given herein are believed to be correct to the best of applicant's knowledge at the present date.
The first modification relates to changing the profile of the leading edge of the wing of the Beaver and Otter aircraft. By adding a cuff of 2024 T3 aluminum having a thickness of 0.032 inches to the leading edge of the wing in a profile as described hereafter, the flight characteristics of the aircraft are enhanced. A plurality of blocks made from FR 3720 polyurethane foam having the desired contour are mounted to the leading edge of the original wing. The aluminum material is then fitted over the blocks and attached to the wing. Suitable provisions are made in the modification for the pitot tube, inboard fairings, air intake and landing lights, all as will be described.
A second modification relates to a droop wing tip modification used to cover the original wing tip tank and is also applicable to both aircraft. The wing tip modification is made from S Class fibreglass. It is intended to fit smoothly with the leading edge modification and has a notable change in configuration from the original which leads to the "droop" modifier. Suitable provisions are made for the navigation light, the filler cap and the drain, all as will be described.
A third modification relates to a flap gap seal modification. This installation is used to cover the gap between the flap and the trailing edge of the wing. The flap gap seal prevents the passage of a large portion of moving air through the gap when the flap is moved to its extended position and is applicable only to the Beaver aircraft. The seal assists the stability of the aircraft in flap extended flight and enhances the takeoff and general flight characteristics in conjunction with the other modifications made to the leading edge of the wing and to the droop wing tip.
A fourth and final modification relates to a stall fence installed on the top of the wing just outside the flap area. This modification is likewise applicable only to the Beaver aircraft.